实现JavaScript图片放大镜效果-优快云博客

本文链接：https://blog.youkuaiyun.com/pe11223/article/details/128706791

需求
1.鼠标移至图片上方，鼠标周围出现黄色的的正方形框，黄色矩形框会随着息标的移动而移动:
2.将黄色正方形框里的内容的长和宽均放大2.4倍，并在图片右边进行显示。
原理
主要就是获取鼠标数据，取得鼠标移动数值，移入黄色框和大图显示，移出则不显示。
利用this取值，鼠标左右给值。
代码

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        .top{
            height: 150px;
            background-color: black;
            color: white;
            font-size: 50px;
            text-align: center;
            line-height: 150px;
            margin-bottom: 100px;
        }
        #box{
            height: 400px;
            width: 700px;
            float: left;
            position: relative;
        }
        #box img{
            display: inline-block;
            height: 400px;
            width: 700px;
        }
        #box2{
            width: 450px;
            height: 450px;
            overflow: hidden;
            float: left;
            position: relative;
        }
        #sm{
            width: 180px;
            height: 180px;
            background-color: yellow;
            opacity: 0.3;
            position: absolute;
            top: 0;
            left: 0;
        }
        #photo{
            position: absolute;
            top: 0;
            left: 0;
        }
        .active{display: inline-block;}
        .end{display: none;}
    </style>
    <title>Document</title>
</head>
<body>
    <div class="top">JS放大镜</div>
    <div id="box">
        <img src="./b.jpg" alt="">
        <div class="end" id="sm"></div>
    </div>
    <div id="box2" class="end">
        <img src="./b.jpg" alt="ph" id="photo">
    </div>

    <script>
        var box = document.getElementById("box");
        var box2 = document.getElementById("box2");
        var sm = document.getElementById("sm");
        var photo = document.getElementById("photo");
        var cleft=0,ctop=0,x=0,y=0,m=0,n=0;

        box.onmouseenter = function(){
            box2.className="active";
            sm.className="active";
        }
        
        box.onmouseleave = function(){
            box2.className="end";
            sm.className="end";
        }

        sm.onmousedown = function(e){
            x =e.clientX-this.offsetLeft;
            y =e.clientY-this.offsetTop;

            document.onmousemove = function(e){
                cleft =e.clientX-x;
                ctop =e.clientY-y;
                if(cleft<=0){
                    cleft=0;
                }
                if(cleft>=box.offsetWidth - sm.offsetWidth){
                    cleft =box.offsetWidth - sm.offsetWidth;
                }
                if(ctop<=0){
                    ctop=0;
                }
                if(ctop>=box.offsetHeight - sm.offsetHeight){
                    ctop = box.offsetHeight-sm.offsetHeight;
                }
                m = -(parseInt(((photo.offsetWidth+x)/box2.offsetWidth)*cleft));
                n = -(parseInt(((photo.offsetHeight+y)/box2.offsetHeight)*ctop));
                sm.style.left = cleft+"px";
                photo.style.left = m+"px";
                sm.style.top = ctop+"px";
                photo.style.top = n +'px';
            }.bind(this)
            document.onmouseup = function(e){
                document.onmousemove = "null";
                document.onmouseup = "null";
            }
        }
    </script>
</body>
</html>

效果

JS案例：放大镜效果